The fight over President Donald Trump's plan to ban temporarily people entering the United States from six predominantly Muslim countries has now boiled down to whether the conservative-leaning U.S. Supreme Court will allow the controversial executive order to go into effect immediately despite being blocked by lower courts.

The fight over President Donald Trump’s plan to ban temporarily people entering the United States from six predominantly Muslim countries has now boiled down to whether the conservative-leaning U.S. Supreme Court will allow the controversial executive order to go into effect immediately despite being blocked by lower courts.

Arguing that the temporary ban is urgently needed to protect Americans from terrorist attacks, the government has asked the court to stay quickly the lower court actions. If the court agrees, a 90-day ban on people entering the United States from Iran, Libya, Somalia, Sudan, Syria and Yemen will be immediately revived. The court could also put a 120-day ban on all refugees into effect and allow the administration to consider new vetting procedures.

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Even if the court allows the travel ban to take effect, the bigger constitutional questions of religious discrimination and presidential powers raised by the March 6 order would not be considered by the nine justices until long after the ban periods have ended. The court begins its summer recess at the end of this month and would not give the case a full hearing until its return in the fall, by which time the ban would have lapsed.

The administration filed emergency applications with the high court on Thursday night seeking to block injunctions issued by judges in Maryland and Hawaii. The Maryland order was upheld on May 25 by the 4th U.S. Circuit Court of Appeals in Richmond, Virginia. The government’s appeal of the Hawaii injunction is currently being considered by the San Francisco-based 9th U.S. Circuit Court of Appeals. That court could issue its decision before the Supreme Court acts on the emergency application.

The high court has a 5-4 conservative majority, with the administration needing five votes to put the ban into effect. Several factors are weighed when the court considers emergency applications, which are rarely granted. One notable example of a successful emergency application was when the court in February 2016 granted on a 5-4 vote a request by states and industry groups to block President Barack Obama’s climate regulations.

So far the travel ban has been litigated in courts dominated by Democratic-appointees. While it has not fared well legally, experts point out that the Supreme Court presents the best chance the administration has to notch up a win.

“Even though it’s a heavy lift getting a stay, it seems to me that the Supreme Court is the most favorable court they’ve had access to so far,” said John Elwood, a Washington lawyer.

The first step for the court will be to ask the various challengers, including the American Civil Liberties Union and Hawaii, to file responses to the Trump administration’s application. The administration is then likely to file its own response to the challengers’ legal arguments before the justices issue an order granting or denying the application. That could happen within days.

Under Supreme Court precedent, several criteria need to be met for an emergency application to be granted, including that there will be “irreparable harm” if it is denied and that there is a “reasonable probability” that the court would agree to hear the case on the merits.

In Thursday’s court filings, Acting Solicitor General Jeff Wall wrote that all the boxes have been checked. The nationwide injunctions blocking the travel ban have caused irreparable harm by “preventing the executive from effectuating his national-security judgment,” he wrote. As the case “enjoins a formal national-security determination by the president of the United States” there is also a strong likelihood the court would want to take the case, he added.

CHALLENGERS DISPUTE URGENCY

The challengers contest the administration’s claim that urgent action is needed for national security reasons. They point to the fact that the government did not previously ask the Supreme Court to intervene, even when lower courts denied earlier emergency applications seeking to lift the injunctions.

“This is different from the kind of case you would expect the Supreme Court to grant the extraordinary relief of a stay, because of the lack of any demonstrable urgency or harm and because the law and the facts are on our side,” said ACLU lawyer Omar Jadwat.

One thorny issue the Supreme Court may have to resolve if it grants the stay is whether the 90-day ban would begin from the day of the court’s action or whether the clock has been ticking throughout the litigation, in which case it would expire in mid-June. Challengers will argue for the latter, which would mean it is almost set to expire. That would limit the practical impact if the application were granted.

The court’s conservative majority includes Justice Anthony Kennedy. He sometimes sides with the court’s four liberals and could be the pivotal vote.

The travel ban’s challengers have relied in part on a concurring opinion Kennedy wrote in a 2015 Supreme Court immigration case. Kennedy wrote that in the immigration context, the government’s actions can be questioned if there is evidence of bad faith.

Another conservative justice is the man Trump recently appointed to the high court, Neil Gorsuch. During his Senate confirmation hearing, Gorsuch insisted he would not be a rubber stamp for any president when asked about Trump’s statements criticizing judges who ruled against the travel ban.

Separate from the emergency application, the court also has to decide whether to hear the government’s full appeal of the Virginia-based appeals court ruling.

The justices are not required to hear any case, but this one meets important criteria cited by experts, including that it is the federal government filing the appeal and that it involves a nationwide injunction.